Abstract
BackgroundAlterations in the fecal bacterial flora occur in inflammatory bowel disease (IBD). We examined the abundance and diversity of Clostridium leptum group, an important group of carbohydrate-fermenting bacteria, in the feces of patients with IBD and compared them with healthy controls.MethodsSeventeen healthy controls (HC), 20 patients with Crohn’s disease (CD) and 22 patients with ulcerative colitis (UC) participated in the study. DNA extracted from fecal samples was amplified by PCR targeting 16S rRNA gene sequences specific to C. leptum group. The PCR product was subjected to temporal temperature gradient electrophoresis (TTGE) and the number and position of individual bands were noted and diversity was estimated. The identity of bands at different positions was confirmed by cloning and sequencing. Real time quantitative PCR with Mesa Green, targeted at specific 16S rRNA gene sequences, was used to quantitate C. leptum group and its most prominent constituent, Faecalibacterium prausnitzii.ResultsTwenty five different operational taxonomic units (OTUs, equivalent to species) were identified constituting the C. leptum group in these participants. Their sequences were deposited in GenBank [accession numbers GQ465348 to GQ465370]. OTU number was significantly reduced in CD (7.7±3.7, mean±SD) and UC (9.0±3.0) compared to HC (11.9±2.2) (P=0.0005). The Simpson D index of alpha diversity was not significantly different between the three groups. Total numbers of C. leptum group bacteria and F. prausnitzii were reduced in both CD and UC compared to HC (P=0.0036 and P<0.0001 respectively). Disease activity did not influence numbers of C. leptum or F. prausnitzii in patients with CD or UC.ConclusionC. leptum numbers and diversity were significantly reduced in both CD and UC suggesting that alterations noted were not specific to one disease. This could contribute to reduced short chain fatty acid production in IBD.
Highlights
Alterations in the fecal bacterial flora occur in inflammatory bowel disease (IBD)
In the present study we investigated the species diversity of the C. leptum group of bacteria in the feces of healthy individuals and patients with IBD in remission using amplification of the 16S rRNA gene followed by temperature gradient electrophoresis
Diversity indices based on temperature gradient electrophoresis (TTGE) profile The number of C. leptum group species (Figure 4) was significantly less in Crohn’s disease (CD) and ulcerative colitis (UC) compared to healthy controls (HC)
Summary
Alterations in the fecal bacterial flora occur in inflammatory bowel disease (IBD). We examined the abundance and diversity of Clostridium leptum group, an important group of carbohydrate-fermenting bacteria, in the feces of patients with IBD and compared them with healthy controls. The Clostridium leptum group of bacteria is one of the dominant groups of fecal bacteria in adult humans, constituting 16-25% of the fecal microbiota [1,2]. This group, called Clostridial cluster IV, includes Faecalibacterium prausnitzii and certain species of Eubacterium and Ruminococcus [3]. Members of this group synergize with other intestinal microbiota to ferment unabsorbed dietary carbohydrate, producing short chain fatty acids of which butyrate is the major energy source for the colonic epithelium and profoundly influences intestinal epithelial function. Any alteration in the composition of the gut microbiota that changes the microbial balance is likely to have repercussions on human health
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